Date of Award
Doctor of Philosophy (PhD)
Dr. H.E. Schellhorn
Many factors regulate the expression of rpoS at the levels of transcription, translation, proteolysis and RpoS activity. However, the relative importantance of different levels of control is not well understood. By manipulating rpoS expression, we will better understand environmental adaption responses. The first part of the study suggests that RpoS mutants can be selected using minimal media supplemented with succinate. We isolated 20 mutants that had the ability to grow on succinate as the sole carbon source. All mutants exhibited lower levels of RpoS function or osmY transcription. Sequencing and alignment analyses confirmed that all isolated succinate utilizing mutants possessed mutated alleles of the rpoS gene. Succinate transvertion mutant can revert to an rpoS wild type phenotype under sub-optimal conditions.
The second part of the study has demonstrated that inducible rpoS antisense RNA complementary to rpoS mRNA can inhibit the expression of RpoS in both exponential and stationary phases and can attenuate expression of the rpoS regulon in E. coli.
The final part of the study artificially expressed RpoS protein and its regulon in both exponential and stationary phases. rpoS mRNA can be induced at an early stage of cell growth when RpoS levels are normally extremely low (i.e., in early exponential phase) and can activate the expression of the RpoS regulon in exponential phase and stationary phase. Our results showed that controllable levels of RpoS could regulate the expression of rpoS and RpoS-dependent genes indicating RpoS expression is sufficient for expression of the regulon in exponential phase.
Chen, Guozhu, "Studies on the Control of Gene Expression of rpoS and its Regulon in Escherichia Coli" (2003). Open Access Dissertations and Theses. Paper 919.